TWI398193B - Induktionsheizspule und verfahren zum schmelzen von granulat aus halbleitermaterial - Google Patents

Description

Inductive heating coil and method of melting particles composed of semiconductor material

The present invention relates to an induction heating coil and a method of melting particles composed of a semiconductor material on a plate having an outlet conduit. According to DE 102 04 178 A1, an induction heating coil of this type is required in order to be able to produce a single crystal of a semiconductor material from particles.

Figure 4 shows a known induction heating coil in a device for producing a single crystal process. With the aid of the induction heating coil, the molten particles flow through the opening in the center of the plate to form a funnel-shaped film of semiconductor material that becomes molten. The melt forms a reservoir that crystallizes on a single crystal and simultaneously increases its volume through the control of a traction coil. Maintaining a liquid state is important for crystal growth processes without any interference, especially for films and adjacent melts. A radiant heating system is provided to avoid uncontrolled solidification of the film and melt. However, such a radiation heating system is both complicated and is not very effective because most of the radiation impinging on the film is reflected, so that it is still ineffective. In addition, since the respective incident angles of the radiation are significantly different, the film and the melt cannot be uniformly heated.

It is an object of the present invention to achieve a uniform heating of the film and adjacent melts more simply and efficiently.

The present invention relates to an induction heating coil for melting particles composed of a semiconductor material on a plate having an outlet pipe, the heating coil comprising a coil body having a flow guiding groove, the coil body having an upper side and a lower a side of the side of the coil body having a particle passage opening in a region outside the center of the coil; and a current-carrying portion projecting from a center of a lower side of the coil body, the current-carrying portions passing through a mesh of the lower end and being electrically conductive connection.

The invention also relates to a method of melting particles composed of a semiconductor material by means of an induction heating coil on a plate having an outlet conduit, comprising forming a film of molten semiconductor material which wets the outlet conduit; a melt of a semiconductor material having a free surface surrounded by the film, wherein the film and the melt are tied to the region of the free surface, heated by means of a current carrying portion, the current carrying portions protruding from the The center of the lower side of the induction heating coil is electrically connected through a mesh of the lower end.

In accordance with the present invention, an induction heating coil for melting particles can also be used to inductively heat the film and the adjacent upper region of the melt and maintain it in a liquid state. This makes it possible to ensure that a continuous and controllable melt flows from the plate to the single crystal. For this purpose, the coil body has current-carrying segments protruding from the center of the lower side of the coil body, the current-carrying portions projecting into a film of semiconductor material facing the side and melting at the bottom In the channel defined by the object. The current carrying portions are preferably arranged such that induction heating of the film and the melt is particularly effective in the free surface area of the melt surrounded by the film. The shape of the current-carrying portions based on filling the volume of the channel almost completely by the current-carrying portions is particularly preferred. Therefore, the current-carrying portions are formed, for example, into two current-carrying portions which are formed in a truncated cone shape and are electrically connected to each other through a mesh at the lower end thereof.

This and other features of the present invention will be described in more detail below with the aid of the drawings. The induction heating coil is formed by the fact that the RF current flows substantially through the coil body 1 and the current carrying portion 2 (Figs. 2 and 3). The current-carrying portions 2 are electrically connected to each other through a thin mesh 3 at the lower end thereof. The coil main body 1 has a radial flow guiding groove 4 that suppresses a current from flowing through the coil main body 1 from the meandering path. The path is from the coil connector 5 at the edge of the coil body 1 to the current-carrying portion 2 at the center of the coil, passes through the carrier portion 2 and passes through the coil body 1, and returns to the coil connector 5. In this way it is ensured that all areas of the surface of the panel 9 are uniformly covered by an electromagnetic field in which the electromagnetic field induced current can melt the particles 13 and maintain the molten state.

The coil body 1 has at least one passage opening 6 in its outer region to convey particles composed of a semiconductor material onto the rotating plate 9. The passage opening 6 is preferably formed by a flow guiding groove 4 which is partially widened for this purpose. The induction heating coil is further equipped with a cooling system comprising a cooling passage 7 in the coil body 1 in which a coolant (e.g., water) flows ^. Further, in order to strengthen the cooling current-carrying portion 2, the cooling passages 7 are led to the current-carrying portions 2 and are connected to each other through the tube bridge 8. The tube bridge 8 extends to the center of the upper side of the coil body 1 and as far as the current carrying portions 2, and is connected thereto by, for example, soldering or direct soldering. The tube bridge 8 is single-wound or multi-wound so that it has a sufficiently high induction. The RF current thus flows substantially through the mesh 3 connecting the current carrying portions 2, rather than through the tube bridge 8. By means of the current flow, the intensity of the field lines in the region of the mesh 3 is particularly high, and the induction heating of the melt directly opposite the mesh 3 during the production of the single crystal 10 is particularly effective. The melt and the web 3 are preferably at the same potential, particularly preferably at ground potential.

Figure 1 shows a preferred arrangement of the induction heating coil and plate 9 during the production of the single crystal 10. The current-carrying portion 2 forms a frustum and extends almost to the melt in the region of the mesh 3. The film 12 of molten semiconducting material flowing out of the outlet duct 11 of the plate 9 encloses a passage whose volume is almost completely filled by the current-carrying portions 2. Preferably, the inclination angle of the outer surface of the current-carrying portion 2 is the same as the inclination angle of the inner surface of the outlet duct 11. The continuous flow of molten semiconductor material from the plate 9 to the melt can be additionally improved by the truncated cone, which is placed in the channel in a slightly asymmetrical manner and thus a side is better heated. Thus, when only a small melt flow is required, a defined closed melt path can be formed at the beginning of the growth process.

The plate 9 is preferably composed of the same semiconductor material as the particles 13, and is preferably embodied in a similar manner to the container described in DE 102 04 178 A1, the disclosure of which is incorporated herein by reference. However, especially if it is used to melt particles to form a single crystal having a relatively small diameter, it can also be embodied as a simple plate having a central outlet pipe. The component symbol 14 represents a funnel into which the particles 13 are transferred.

The invention is preferably used to make a single crystal composed of tantalum. Semiconductor wafers cut from a single crystal are suitable for fabricating, for example, solar cells or electronic components such as power transistors and thyristors.

Example:

Using the induction heating coil according to the invention as set forth in Figure 1, a single crystal of tantalum can be fabricated without the need to provide a radiant heating system for the channel and adjacent melt. Since the lanthanide crystallizes within the film or in the contiguous region of the melt, the single crystal grown by the pull is free of dislocation and has no yield loss.

1. . . Coil body

2. . . Current carrying part

3. . . Mesh

4. . . Guide groove

5. . . Coil connector

6. . . Channel opening

7. . . Cooling channel

8. . . Pipe bridge

9. . . board

10. . . Single crystal

11. . . Export pipeline

12. . . film

13. . . Granule

14. . . Funnel

1 is a schematic longitudinal cross-sectional view of an induction heating coil in accordance with a preferred embodiment of the present invention in a device for producing a single crystal process;

Figures 2 and 3 show a plan view and a cross-sectional view of the induction heating coil;

Fig. 4 is a cross-sectional view showing the prior art corresponding to Fig. 1.

1. . . Coil body

2. . . Current carrying part

3. . . Mesh

5. . . Coil connector

6. . . Channel opening

7. . . Cooling channel

8. . . Pipe bridge

9. . . board

10. . . Single crystal

11. . . Export pipeline

12. . . film

13. . . Granule

14. . . Funnel

Claims (9)

An induction heating coil for melting particles composed of a semiconductor material on a plate having an outlet pipe, the heating coil comprising a coil body having current-guiding slots, the coil body having an upper side And a side surface of the coil body having a particle passage opening in a region outside the center of the coil; and a current-carrying segment protruding from a center of a lower side of the coil body, the current-carrying portions passing through the lower end One of the meshes is electrically connected. The induction heating coil of claim 1, wherein at least one of the flow guiding grooves is widened to form the passage opening. The induction heating coil of claim 1 or 2, wherein the current-carrying portions form a truncated cone shape. The induction heating coil of claim 1 or 2, wherein an outer surface of the current-carrying portion has an inclination angle equal to an inclination angle of an inner surface of the outlet duct. The induction heating coil of claim 1 or 2, comprising a cooling system for cooling the coil body and the current carrying portions. The induction heating coil of claim 5, wherein the cooling system comprises a wound tube bridge through which a coolant flows, and the tube bridge and the current carrying portion are tied to a center of the upper side of the coil body contact. A method of melting particles of a semiconductor material by means of an induction heating coil on a plate having an outlet conduit, comprising forming a film of molten semiconductor material that wets the outlet conduit; and forming a film by the film a melt of a semiconductor material having a free surface, wherein the film And the melt is heated at a region of the free surface by means of a current-carrying portion protruding from a center of a lower side of the induction heating coil and electrically connected through a mesh of the lower end. The method of claim 7, wherein the particles and the plate are each composed of ruthenium. The method of claim 7 or 8, wherein the mesh and the melt are at the same potential.